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IX. — On the Dynamical Theory of Heat. Part V. Thermo-electric Currents. 

 By William Thomson, M.A., Professor of Natural Philosophy in the Uni- 

 versity of Glasgow. 



(Read 1st May 1854.) 



Preliminary §§ 97-101. Fundamental Principles of General Thermo-dynamics 



recapitulated. 



97. Mechanical action may be derived from heat, and heat may be generated 

 by mechanical action, by means of forces either acting between contiguous parts 

 of bodies, or due to electric excitation ; but in no other way known, or even con- 

 ceivable, in the present state of science. Hence Thermo-dynamics falls naturally 

 into two Divisions, of which the subjects are respectively, the relation of heat 

 to the forces acting between contiguous parts of bodies, and the relation of heat to 

 electrical agency. The investigations of the conditions under which thermo- 

 dynamic effects are produced, in operations of any fluid or fluids, whether 

 gaseous or liquid, or passing from one state to the other, or to or from the 

 solid state, and the establishment of universal relations between the physical 

 properties of all substances in these different states, which have been given 

 in Parts I.-V. of the present series of papers, belong to that first great Division 

 of Thermo-dynamics — to be completed (as is intended for future communica- 

 tions to the Royal Society) by the extension of similar researches to the thermo- 

 elastic properties of solids. The second Division, or Thermo-electricity, which 

 may include many kinds of action as yet undiscovered, has hitherto been investi- 

 gated only as far as regards the agency of heat in producing electrical effects in 

 non-crystalline metals. In a mechanical Theory of electric currents, communi- 

 cated to the Royal Society, Dec. 15, 1851,* the application of the General Laws 

 of the Dynamical Theory of Heat to this kind of agency was made, and certain 

 universal relations precisely analogous to the thermo-elastic properties of fluids 

 established in the previous treatment of the First Division of the subject, were 

 established between the thermo-electric properties of non-crystalline metals. The 

 object of the present communication is to extend the theory to the phenomena of 

 thermo-electricity in crystalline metals ; but as recent experimental researches on 

 air have pointed out an absolute thermometric scale,f the use of which in express- 



* See " Proceedings" of that date, or Philosophical Magazine, 1852, where a sufficiently complete 

 account of the investigations and principal results is given. 



"j" That is a scale defined without reference to effects experienced by any particular kind of matter. 

 Such a scale, founded on general thermo-dynamic relations of heat and matter, and requiring reference 

 to a particular thermometric substance only for defining the unit or degree, was, so far as I know, 



VOL. XXI. PART I. 2 L 



